I. Field of the Invention
The present invention relates generally to wireless communication systems and more particularly to a method and apparatus for automatically detecting vehicle arrival and departure events using a wireless communication system.
II. Description of the Related Art
The use of wireless communication systems is well known for transmitting information between fixed stations and one or more geographically dispersed mobile receivers. For example, satellite communication systems have been used in the trucking industry for many years to provide messaging and location information between fleet-owned dispatch centers and their respective tractor-trailer vehicles. Such systems offer significant benefits to fleet owners because they allow almost instantaneous communications and real-time position information. In addition, many such systems provide remote monitoring of the performance characteristics of each fleet-owned vehicle, such as the average speed, RPM, and idle time of each vehicle. An example of such a satellite communication system is disclosed in U.S. Pat. No. 4,979,170 entitled "ALTERNATING SEQUENTIAL HALF DUPLEX COMMUNICATION SYSTEM AND METHOD", U.S. Pat. No. 4,928,274 entitled "MULTIPLEXED ADDRESS CONTROL IN A TDM COMMUNICATION SYSTEM", and U.S. Pat. No. 5,017,926 entitled "DUAL SATELLITE NAVIGATION SYSTEM", assigned to the assignee of the present invention and incorporated by reference herein.
In the satellite communication system described by the above-mentioned patents, fleet-owned dispatch centers communicate using land-based systems such as telephone or fiber-optic networks to a hub, otherwise known as a network management facility (NMF). The NMF acts as a central communication station through which all communications between vehicles and dispatch centers pass. The NMF comprises a number of network management computers (NMCs), each NMC responsible for providing a communication path from the NMF to geographically dispersed vehicles in the communication system using a geosynchronous satellite. The geosynchronous satellite comprises one or more transponders, which are electronic circuits well known in the art for relaying high frequency satellite communication signals between remote locations. Each NMC is assigned an individual transponder, each transponder operating at a unique frequency in order to avoid interference with communication signals on other transponders. In the satellite communication system of the above-referenced patents, each transponder is capable of handling the communications needs of approximately 30,000 vehicles.
Each vehicle in the communication system is equipped with a transceiver, otherwise known as a mobile communication terminal (MCT), for communicating message and location information to a pre-designated NMC via the geosynchronous satellite. The MCT typically also comprises an interface device which displays text messages to one or more vehicle occupants and accepts either voice or text messages to be transmitted to the vehicle's fleet-owned dispatch center. Furthermore, the MCT may further comprise a digital processor which communicates with one or more Electronic Control Units (ECUs) located at various points throughout the vehicle. Each ECU provides information relating to the operational performance of the vehicle to the digital computer indicating characteristics including, but not limited to, vehicle speed, engine RPM, and miles traveled.
The wireless communication system described above allows vehicle occupants to easily contact their respective dispatch centers in order to keep fleet personnel apprised of various events throughout a typical delivery cycle. For example, upon arrival at a predetermined pickup destination, a truck driver may contact a dispatch center associated with the vehicle to alert fleet personnel of the time and location of the arrival. Similarly, after the truck has been loaded at the pickup destination, the driver may send a message to the dispatch center indicating the time of departure, the location from where the departure occurred, and a description of the goods that is being transported. Another example where a vehicle operator might transmit a status message to the dispatch center is when an unscheduled stop has been made and/or when the vehicle departs from the unscheduled stop.
Although communications between drivers and dispatch centers have been made much more convenient and reliable using satellite or terrestrial-based communication systems, a variety of problems persist in the reporting process. For example, a driver may forget to send a message upon arrival or departure from a planned pickup destination, causing confusion at the dispatch center as to the status of goods in transit. Or, a driver may send a message long after he has departed a pickup indicating that he is just now leaving the pickup location, to avoid possible negative consequences of forgetting to send a timely message. Furthermore, a driver may not wish to inform the dispatch center when making an unscheduled stop, for a variety of reasons.
The dispatch center relies heavily on driver messages for maximizing fleet efficiency. Therefore, a system is needed that can determine the status of a vehicle in transit without driver intervention. The system should be able to distinguish several different kinds of events, such as arrivals and departures from planned and unplanned stops.